Electron and photons time of flight

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Discussion Overview

The discussion revolves around the comparison of time of flight for photons and electrons, particularly in astrophysical contexts. Participants explore the implications of mass on travel speed, the effects of energy on time delays, and potential sources of data for these comparisons.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants note that photons, having no mass, travel at the speed of light (c), while electrons, being massive, travel at speeds less than c, suggesting a fundamental difference in their time of flight.
  • One participant proposes that the delay in arrival times of massive particles and photons from a distant astronomical source should correlate with their energy, referencing the E(v) relation from Special Relativity.
  • Concerns are raised about the dispersion of charged particles compared to neutral particles, with a mention of the longer lifetimes of certain particles like electrons and protons, while noting the short lifetime of neutrons.
  • Another participant provides a specific example, stating that solar wind electrons travel at 400-750 km/s, which is significantly slower than the speed of light, leading to a much longer travel time compared to photons from the Sun.
  • A later reply questions the necessity of focusing on astrophysical sources, suggesting that similar observations could be made in particle accelerators, where light is observed before charged particles during events like arcing.

Areas of Agreement / Disagreement

Participants express differing views on the relevance of astrophysical sources versus experimental settings, and there is no consensus on the implications of the time of flight differences between photons and electrons.

Contextual Notes

Participants acknowledge various factors that could affect the comparison, such as the energy of the particles, their dispersion, and the specific conditions under which they are emitted. The discussion does not resolve these complexities.

Who May Find This Useful

Readers interested in the physics of particle dynamics, astrophysics, and the implications of mass on travel speeds may find this discussion relevant.

lalbatros
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Hello,

I would be interrested by some references comparing times of flight for photons and electrons.
Ideally, I would like to see that for different energies.
I would also prefer astrophysical sources, since the huge distances should increase the precision.

Thanks
 
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Photons have no mass, and travel at c. Electrons have a small mass and can travel at any speed less than c. Perhaps you meant electrons from some specific source.
 
Let's consider massive particles and photons emitted at the same time from a very distant astronomical source.
The delay between these pulse should be related to the energy of the particles.
I wonder if such data would be available.
In principle this should match the E(v) relation from Special Relativity.

However, there are difficulties:

- charged particles are likely much more dispersed than neutral particles, but they may have longed lifetimes, e-, p+
- neutrons have a lifetime of only 15 min roughly, they could not come from very far

Maybe solar events could be canidates?
 
Wikipedia says that solar wind is 400-750 km/s. That is 0.25% of c. So it would take 400 times as long for electrons from solar wind to travel as photons from the Sun.
 
lalbatros said:
Hello,

I would be interrested by some references comparing times of flight for photons and electrons.
Ideally, I would like to see that for different energies.
I would also prefer astrophysical sources, since the huge distances should increase the precision.

Thanks

Er... why does this have to be "astrophysical sources"? In a particle accelerator, when an arcing occurs during, say, conditioning, you always get the light first and then the burst of charge later.

Is there something that you are trying to get at? I mean, it appears as if this is rather obvious and isn't even a "relativity" issue.

Zz.
 

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